A lithium secondary battery has high energy density per volume or mass by virtue of characteristics of its constituent materials, as compared to a nickel-cadmium battery, a nickel-hydrogen battery, or the like. Accordingly, the lithium secondary battery enables extraction of a large amount of energy from a small battery. In addition, the battery has a high voltage of about 3.7 V, and hence can provide a large amount of power.
Therefore, the lithium secondary battery is currently in wide use as a power source for, for example, a mobile phone, a smartphone, a tablet PC, or a notebook PC.
Characteristics required of the lithium secondary battery include safety, long life, and low price.